Replicative virus-based therapies (virotherapy) for advanced cancer have been clinically studied in recent years. Virotherapy is a therapeutic strategy in which tumor cells are infected with a replicative virus, such as HSV-1 and adenoviruses, to cure tumors by the cell-killing effect of the is associated with the virus propagation When HSV-1 or an adenoviras is used as the replicative virus for antitumor therapy, the virus is a mutant whose viral genome has been altered by genetic manipulation, such that it retains the ability to replicate in tumors while its pathogenicity to normal human tissues has been minimized. The therapeutic replicative viruses that infect tumor cells replicate in the cells, and infected cells are killed during this process. The propagated viruses again infect nearby tumor cells and thus the antitumor effect spreads (Alemany R. et al., Replicative adenoviruses for cancer therapy. Nat Biotechnol., 2000, 18:723-727; Curiel, D. T., The development of conditionally replicative adenoviruses for cancer therapy, Clin Cancer Res., 2000, 6:3395-9; Kim, D., Virotherapy for cancer: Current status, hurdles, and future directions, Cancer Gene Therapy, 9:959-960, 2002; Mineta T. et al., Attenuated multi-mutated herpes simplex virus-1 for the treatment of malignant gliomas. Nat Med 1:938-943, 1995). Anticancer virotherapy can be used in combination with convention therapeutic methods, such as surgery, radiation therapy, and chemotherapy, and is practically superior because of its wide applicability: it is generally applicable to solid cancers; the virus can be repeatedly administered; and the antitumor effect can be potentiated by directly inserting therapeutic genes, such as those encoding cytokines, into the viral genome; and so on. The development of more effective virotherapy is expected to significantly contribute to anticancer treatment.    Non-Patent Document 1: Alemany R. et al., Replicative adenoviruses for cancer therapy. Nat Biotechnol., 2000, 18:723-727    Non-Patent Document 2: Curiel, D. T., The development of conditionally replicative adenovirwes for cancer therapy, Clin Cancer Res, 2000, 6:3395-9    Non-Patent Document 3: Kim, D, Virotherapy for cancer: Current status, hurdles, and fixture directions, Cancer Gene Therapy, 2002, 9:959-960    Non-Patent Document 4: Mineta T. et al., Attenuated multi-mutated herpes simplex virus-1 for the treatment of malignant gliomas. Nat Med, 1995, 1:938-943